The present invention relates to an electric source control system of an information processing system for controlling the information processing system. In particular, the present invention relates to a technique effective when it is applied to an electric source control system of an information processing system having a main electric source and an auxiliary electric source and capable of throwing and cutting an electric source of the information processing system according to an order from a terminal device located in a remote place and connected to the information processing system via a communication line.
To control an electric source in a conventional information processing system, an electric source controller for connecting and disconnecting or throwing and cutting an electric source of the information processing system is provided and the electric source controller is controlled directly by a central processing unit to connect and disconnect the electric source of the information processing system.
As for a technique of this kind, there is described in JP-A-56-166522 a technique for automating the electric source control such as connection and disconnection of an electric source of each device included in an information processing system.
In summary, a system electric source controller has a circuit for generating a power ON signal and a power OFF signal for each device included in the information processing system, and a circuit for generating a first interrupt signal requesting start-up operation and a second interrupt signal requesting start of an information protection program. By sending the power ON signal, the power OFF signal, a ready signal indicating that the device can be used, and an electric source interruption request signal via different signal cables connecting the system electric source controller to respective devices forming a processor and peripheral devices, connection and disconnection of each device forming the information processing system are conducted automatically.
Furthermore, as for a technique concerning the control of a backup electric source at the time of an electric power failure, there is a technique described in JP-A-56-110117.
In summary, devices forming an information processing system are classified into a device group A requiring the power supply even at the time of an electric power failure and a device group B for which suspension of power supply is unavoidable. To devices of the device group B, their electric source is connected without fail via an electric source control circuit. A routine for conducting a task by using only devices of the device group A is incorporated into a CPU as software. At the time of an electric power failure, electric power is supplied to the CPU from a backup electric source. Due to an interrupt conducted by an interrupt generation circuit, the CPU then switches its task to the routine to be used at the time of an electric power failure. In addition, the electric source control circuit stops supply of electric power to the devices belonging to the device group B to reduce the power dissipation of the electric source. Backup of the electric source for a long time is thus effected.
It is now assumed that an electric power failure occurs in the electric source control system of the information processing system using the above described conventional technique and supply of electric power to the information processing system is suspended. Even in the case where electric power can be supplied by a built-in auxiliary electric source at the time of an electric power failure, it is difficult to supply electric power from the auxiliary electric source for a long time. When the capability of electric power supply of the auxiliary electric source has been exhausted, the power supply to the information processing system is suspended. The power supply suspension might be conducted while application software is updating data. This results in a problem of a possibility that important data on the information processing system might be erased or destroyed.
It is assumed again that an electric power failure occurs in the electric source control system of the information processing system using the above described conventional technique and supply of electric power to the information processing system is suspended. Even in the case where electric power can be supplied by a built-in auxiliary electric source at the time of an electric power failure, it cannot be recognized from a terminal device located in a remote place and connected to the information processing system via a communication line that electric power is supplied to the information processing system from the auxiliary electric source. From the terminal device located in the remote place, therefore, it cannot be known that an electric power failure is taking place in the place where the information processing system is installed.
Especially, even when the information processing system is shut down for a reason such as an electric power failure and the electric source turns off, it cannot be grasped in each terminal device that the information processing system cannot continue with processing. Since the situation cannot be grasped on the terminal device side, useless processing and communication for grasping the situation and attempting to start the information processing system are conducted, resulting in a lowered operational efficiency of the system.
Furthermore, the case where recovery from the electric power failure takes place in a short time is also conceivable. Therefore, it is not desirable to start the shutdown processing immediately upon occurrence of an electric power failure.
On the other hand, even if an electric power failure does not occur, it is difficult for a terminal device located in a remote place to know the state of application software which is being executed in the information processing system. While the application software is updating data in the information processing system, therefore, the electric source might be disconnected in the information processing system according to an order issued by a terminal device. Thus there is a possibility that important data on the information processing system might be erased or destroyed.
If control for turning off the electric source of the information processing system is effected by a terminal device located in a remote place, then there is a fear that the data destruction as described above might occur. According to the above described conventional technique, however, it is possible for a terminal device to connect or disconnect the electric source to the information processing system easily.
Furthermore, in the case where the control for turning on and off the electric source is effected by the central processing unit itself as in the conventional technique, it might be disadvantageously disabled to control the electric source or give a notice to a terminal device by a failure of the central processing unit or occurrence of a processing suspension state of the central processing unit caused by application software operating in the central processing unit.